Abstract
Purpose :
We recently demonstrated a significant increase in the circulating levels of 12/15-lipoxygenase (12/15-LO) pro-inflammatory metabolites 12- and 15-HETEs and a contrary decrease in the levels of the anti-inflammatory metabolite resolvin-D2 (RD2) in lipopolysaccharide (LPS)-treated mice. Dietary supplement of docosahexaenoic acid (DHA) restored normal levels of RD2 and attenuated LPS-induced acute kidney injury in mice. The goal of this study was to examine whether RD2 and/or DHA mitigates retinal inflammation using the LPS-induced experimental inflammation model.
Methods :
Five groups of age and weight matched male wild-type (WT) mice were given the respective intraperitoneal injections: 1) saline (control), 2) LPS only (4 mg/kg), 3) LPS+RD2 (100 ng/ mouse), 4) LPS+DHA (50 mg/kg), 5) LPS+Baicalein (20 mg/kg). RD2, DHA, and baicalein, a pharmacological inhibitor of 12/15-LO, were given for 3 days before and 3 days after the single LPS injection. Additionally, three groups of age and weight matched 12/15-LO knockout (KO) mice were given the respective injections: 1) saline (control), 2) LPS (4 mg/kg), 3) LPS+DHA (50 mg/kg). DHA was given for 3 days before and 3 days after the single LPS injection. On day 7, all mice were terminated for retinal tissue collection. The mRNA expression levels of 12/15-LO, TNF-a, IL6, IL10, IL1b and ICAM-1 were analyzed with RT-PCR to determine inflammatory response levels for each group.
Results :
The WT group exposed to LPS showed significant fold increase in 12/15-LO, TNF-a, ICAM-1, IL1b and modest increase in IL6 mRNA expression levels when compared to both the control group and LPS+Baicalein and LPS+DHA group. Moreover, retinal levels of IL10 were restored by baicalein and DHA. While baicalein demonstrated anti-inflammatory effect against LPS, deletion of 12/15-LO did not mitigate the effect of LPS on retinal levels of inflammatory cytokines. Additionally, RD2 abrogated the retinal levels of TNF-a
and ICAM-1 mRNA in LPS-treated mice compared to the control group.
Conclusions :
RD2 and dietary supplementation of DHA are potential therapeutic interventions to treat retinal inflammatory diseases as demonstrated by decreased inflammatory markers after LPS injection. Lack of protection against LPS-induced retinal inflammation in 12/15-LO KO mice suggest that the protective effect of baicalein is independent of its 12/15-LO inhibition effect.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.